Though it was common to make the microwave waveguides with metal, recently, they have also been made of resins.
FIG. 7 shows a prior art waveguide made of a resin (Japanese Patent Application Laid-Open No. 6-104615). This prior art waveguide is manufactured as follows. That is, a base 101 is made of a thermoplastic and, this base 101 has a U-shaped hollow-space 100. Moreover, a cover 103 is also made of a thermoplastic and this cover 103 also has a U-shaped hollow-space 102. The base 101 and the cover 103 are bonded with an epoxy adhesive to form a waveguide 104. A layer of copper is formed on the inner surface of the waveguide 104 by electroless-plating.
In the prior art waveguide, floatings and steps are generated in the base 101 and the cover 103. In other words, the adhesive strength of the adhesive is not sufficient to keep the base 101 and the cover 103 together. To solve this problem and to more tightly hold the base 101 and the cover 103 together, taking into consideration that the waveguide is used in antennas that are installed outdoor and are required to withstand adverse conditions, nuts and bolts (or screws) are provided that hold the base 101 and the cover 103. However, the nuts and bolts make the assembly of the waveguide troublesome.
To correct form errors of a groove (the hollow space) for a waveguide, and deformations of the groove caused by assembling of waveguide units, it is required to adjust a space volume in the inner faces of the groove by using a large number of screws.
It is an object of this invention to produce a waveguide that is easy to assemble, has stronger fastening force between waveguide units, and is air-tight.
It is another object of the present invention to produce a waveguide in which form errors of the groove for the waveguide are fewer, and that can be more efficiently manufactured.